Conventionally, proposed is a system (autonomous cooperative electric power adjustment mechanism) in which multiple devices in systems of breakers autonomously cooperate to automatically adjust used electric power to not exceed a set electric power capacity (see Document 1: Japanese Patent Application Publication No. 2000-137534).
The system disclosed in Document 1 comprises measuring current used in the system, and communication with multiple devices (device agents). The system has an electric power adjuster, which cooperates with the devices to adjust the use amount of current. The electric power adjuster determines, upon receiving a request for required electric power (request for an increase in electric power) from a device, a possibility of permission depending on whether or not a sum of the present use current and the request current is within a threshold value, and if possible, performs permission for an increase in electric power to the original device of a request source.
In contrast, if the electric power adjuster cannot respond to the request for an increase in electric power, the electric power adjuster requests all the devices to suppress the electric power consumption. In this case, devices capable of suppressing the electric power notify the electric power adjuster of information such as the amount of electric power capable of being suppressed. The electric power adjuster decides, on the basis of the notified information, one or multiple devices to be suppressed, and requests the devices to suppress electric power. The devices that receive the request to suppress electric power perform electric power suppression processing. As soon as the electric power requested from the device is secured, the electric power adjuster performs permission for an increase in electric power to the original device of a request source.
In this way, the electric power adjuster can secure the margin electric power, even if there is no margin electric power (surplus current) for an operation of a given device, by performing suppression processing in accordance with the status and the ability for each device.
Meanwhile, in the system disclosed in Document 1, if the electric power adjuster cannot respond to a request from a given device as described above. The electric power adjuster requests all of the devices to suppress electric power, and determines a device wherein the suppression is performed based on information (possible suppression amount of electric power or the like) notified from the devices in response to the request. In this manner, when securing a margin of electric power (“margin electric power,” the electric power adjuster once requests all the devices to suppress electric power. The adjuster selects a device for actual suppression of electric power after receiving information from the respective devices. Accordingly, as the number of devices increase, a longer time for securing the margin electric power is required. Accordingly, the device that requests an increase in electric power might need longer time from issuance of the request until receiving permission for an increase in electric power and starting an operation.